The present invention relates to electrochemical cells and more particularly to electrochemical cells having at least one terminal that prevents the flow of electrical current between that electrochemical cell and another adjacent electrochemical cell aligned in an end-to-end configuration and positioned in the reverse direction relative to the other.
Most conventional electrochemical cells are cylindrical in shape and have a positive terminal at one end and a negative terminal at the other end of the cylindrically shaped housing. Many devices, such as flashlights, require multiple cells, often in a straight-line configuration with the negative terminal of one electrochemical cell contacting the positive terminal of another electrochemical cell. Even though most conventional electrical devices have directions of how to insert the electrochemical cells into the device, occasionally an electrochemical cell is inserted in the reverse direction from that which is intended and proper. This is commonly referred to as cell reversal. The primary danger associated with cell reversal is the possible charging of the reversed cell by two or more other cells during discharge. Such charging can lead to an increase in internal pressure due to the generation of hydrogen gas and may lead to the activation of the safety vent of the electrochemical cell, from which electrolyte or other internal components of the electrochemical cell can leak.
Various attempts have been made to reduce or eliminate the negative effects of cell reversal. Once such approach was taken in U.S. Pat. No. 5,173,371 to Huhndorff et al. The Huhndorff et al. patent discloses a terminal with an electrically non-conductive portion that is cooperatively positioned above an electrically conductive portion. The non-conductive portion may be masked with an electrically non-conductive resin. However, it has been found that during the process of applying the non-conductive material to the terminal, a vacuum was created between the terminal and the application roller. This vacuum caused the non-conductive material to migrate toward the center of the terminal, which is undesirable aesthetically as well as functionally.
Another such attempt to prevent the negative effects of cell reversal was made in Japanese Application No. 09161762 to Fuji Electrochemical Company Ltd. That application shows a battery with a flat surface having three insulated projections to provide a clearance between the flat surface and the negative electrode of another battery. However, with three small projections as shown in this Japan application, only a slight tilting of two cells relative to each other may cause the conductive portion of the terminals to touch. Also, the heights of the insulated projections are difficult to control during the manufacturing process, and if conveyed along a belt during manufacture, the projections may be partly abraded away.
There is a need for a method of making an electrochemical cell with cell reversal protection that has a means for reducing migration of the non-conductive material on the terminal of the electrochemical cell.
One aspect of the present invention is an electrochemical cell comprising a housing having a first end and a second end, a first terminal at the first end of the housing, and a second terminal at the second end of the housing, the second terminal having an a substantially flat portion and a raised portion, the uppermost part of which is insulated, and a passageway at or radially inward of the raised portion to allow air ingress to the radial center of the second terminal when a flat structure is placed against the second terminal parallel to the flat portion.
Another aspect of the present invention is an electrochemical cell comprising a housing having a first end and a second end, a first terminal at the first end of the housing, and a second terminal at the second end of the housing, with the second terminal having a substantially flat portion and a raised portion, the uppermost part of which is insulated, and an air ingress means for allowing sufficient air ingress to avoid migration of a non-conductive coating toward the center of the second terminal from the raised portion during application of the nonconductive material.
Yet another aspect of the present invention is an electrochemical cell comprising a housing having a first end and a second end, a first terminal at the first end of the housing, and a second terminal at the second end of the housing, the second terminal having an exterior surface with an electrically non-conductive raised portion having at least one notch therein.
Yet another aspect of the present invention is an electrochemical cell comprising a housing having a first end and a second end, a first terminal at the first end of the housing, and a second terminal at the second end of the housing, the second terminal having an exterior surface with an electrically non-conductive raised portion and at least one hole therein between the radial center of the second terminal and the raised portion. Yet another aspect of the present invention is a method of making an electrochemical cell comprising the steps of providing a housing having a first end and a second end, a first terminal, and a second terminal having a raised portion; providing at least one notch in the raised portion; coating the raised portion with an electrically insulating material; connecting the first terminal to the first end of the housing; and connecting the second terminal to the second end of the housing.
Still another aspect of the present invention is a method of making an electrochemical cell comprising the steps of providing a housing having a first end and a second end, a first terminal, and a second terminal having a raised portion; providing at least one hole in the second terminal positioned radially between the raised portion and the radial center of the second terminal or at the radial center; coating at least the uppermost part of the raised portion with an electrically insulating material; connecting the first terminal to the first end of the housing; and connecting the second terminal to the second end of the housing.
Yet another aspect of the present invention is an electrochemical cell comprising a cylindrical housing having a first end and a second end; internal components including an anodic material, a cathodic material, and an alkaline electrolyte in the housing; a positive terminal at the first end of the housing; and a negative terminal at the second end of the housing, the negative terminal having an exterior surface with a circular raised portion with a plurality of notches therein, the raised portion being covered by a non-conductive material.
These and other features, advantages and objects of the present invention will be further understood and appreciated by those skilled in the art by reference to the following specification, claims, and appended drawings.